BIOS Power-On Self Test (POST)
This information is taken from various valid sources and its not all in my own words. I'm posting it to hopefully help some1 who has any problems with their comps.
BIOS stands for Basic Input/Output System, although the full term is used very infrequently. The system BIOS is the lowest-level software in the computer; it acts as an interface between the hardware (especially the chipset and processor) and the operating system. The BIOS provides access to the system hardware and enables the creation of the higher-level operating systems (DOS, Windows 95, etc.) that you use to run your applications. The BIOS is also responsible for allowing you to control your computer's hardware settings, for booting up the machine when you turn on the power or hit the reset button, and various other system functions.
IBM
No beep Power supply, system board
1 short beep System OK
2 short beeps POST Error displayed on monitor
Repeating short beeps Power supply, system board
3 long beeps 3270 keyboard card
1 long, 1 short beeps System board
1 long, 2 short beeps Display adapter (MDA, CGA)
1 long, 3 short beeps EGA
Continuous beep Power supply, system board
Note: Some POST errors are considered "fatal" while others are not. A fatal error means that it will halt the boot process immediately (an example would be if no system memory at all is found). In fact, most POST boot errors are fatal, since the POST is testing vital system components
AMI
Beep(s) Failure
1 short DRAM refresh
2 short Parity circuit
3 short Base 64K RAM
4 short System timer
5 short Processor
6 short Keyboard controller Gate A20 error
7 short Virtual mode exception error
8 short Display memory R/W test
9 short ROM BIOS checksum
1 long, 3 short Non-fatal--Conventional/extended memory
1 long, 8 short Non-fatal--Display/retrace test
PHOENIX
Beep Non-Fatal Failures* code
4-2-1 Timer tick interrupt test (or in progress)
4-2-2 Shutdown test (or in progress)
4-2-3 Gate A20 failure
4-2-4 Unexpected interrupt in protected mode
4-3-1 RAM test in progress or address failure > FFFFh
4-3-3 Interval timer Channel 2
4-3-4 Time-of-day clock (or test)
4-4-1 Serial port (or test)
4-4-2 Parallel port (or test)
4-4-3 Math coprocessor (or test)
low 1-1-2 System-board select
low 1-1-3 Extended CMOS RAM
PHOENIX
Beep Fatal Failures* Beep code
1-1-3 CMOS write/read (or real-time clock read/write)
1-1-4 ROM BIOS checksum
1-2-1 Programmable interval timer
1-2-2 DMA initialization
1-2-3 DMA page register write/read
1-2-4 SRAM test and configuration (or test)
1-3-1 RAM refresh verification
1-3-3 1st 64kb RAM chip or data line failure, multibit
1-3-4 First 64K RAM odd/even logic
1-4-1 Address line failure first 64K RAM
1-4-2 Parity failure first 64K RAM
2-1-1 Bit 0 first 64K RAM
2-1-2 Bit 1 first 64K RAM
2-1-3 Bit 2 first 64K RAM
2-1-4 Bit 3 first 64K RAM
2-2-1 Bit 4 first 64K RAM
2-2-2 Bit 5 first 64K RAM
2-2-3 Bit 6 first 64K RAM
2-2-4 Bit 7 first 64K RAM
2-3-1 Bit 8 first 64K RAM
2-3-2 Bit 9 first 64K RAM
2-3-3 Bit 10 first 64K RAM
2-3-4 Bit 11 first 64K RAM
2-4-1 Bit 12 first 64K RAM
2-4-2 Bit 13 first 64K RAM
2-4-3 Bit 14 first 64K RAM
2-4-4 Bit 15 first 64K RAM
3-1-1 Slave DMA register
3-1-2 Master DMA register
3-1-3 Master interrupt mask register failure
3-1-4 Slave interrupt mask register failure
3-2-4 Keyboard controller test failure
3-3-4 Screen initialization
3-4-1 Screen retrace
3-4-2 Search for video ROM in progress (not failure)
DTK/ERSO XT BIOS
1 short Begin POST and End POST
1 long, 1 short Floppy Disk Drive or Controller Failure
Continuous short Parity Error in First 64K RAM
Continuous tone First 64K RAM failure
1 long Keyboard Failed or Locked, Interrupt or other system board error
long short, long short, long short Video Initialization Failure, or Invalid Video Switch Setting
Post Codes for EuroBIOS v4.71
03 DMA Page registers OK
04 DMA Page registers failed
05 Keyboard did reply
06 Keyboard did not reply
07 Keyboard self-test passed
08 Keyboard self-test failed
09 8042 was able to read links
0A 8042 was unable to read links
0B RATMON/DIAG link OK
0C Keyboard accepted 60h command
0D Keyboard did not accept 60h
0E Keyboard parameter accepted
0F Keyboard parameter not accepted
10 Able to read keyboard command byte
11 Unable to read keyboard command byte
12 Keyboard command byte came back OK
13 Keyboard command byte came back corrupt
14 RAM refresh clock ticking correctly
15 RAM refresh clock not ticking correctly
16 RAM bit test passed
17 RAM bit test failed
18 RAM parity OK
19 RAM parity error
1A CMOS RAM passed
1B CMOS RAM failed
1C CMOS RAM battery OK
1D CMOS RAM battery faulty
1E CMOS RAM checksum passed
1F CMOS RAM checksum failed
20 CMOS RAM battery fault bit set
21 DMA controllers passed
22 DMA controller 1 failed
23 DMA controller 2 failed
24 Protected mode entered safely
25 RAM test completed
26 ROM checksum correct
27 ROM checksum incorrect
28 Protected mode exit successful
29 Keyboard power-up reply received
2A Keyboard power-up reply not received
2B Keyboard disable command accepted
2C Keyboard disable command not accepted
2D No video display
2E Reported errors
2F About to halt
30 Protected mode entered safely
31 RAM test complete
32 PIC 1 (master) passed
33 PIC 1 (master) failed
34 PIC 2 (slave) passed
35 PIC 2 (slave) failed
36 Chipset initialised OK
37 Chipset initilize failed
38 Shadowed BIOS OK
39 Shadowed BIOS failed
3A Shadowed video BIOS OK
3B Shadowed video BIOS failed
I hope this helps.
